1. Field of the Invention
The present invention relates to a cutting unit for cutting off material in strip form, preferably paper.
2. Description of the Prior Art
In the known art and in particular in the paper and cardboard article making field there are known cutting units which generally include a usually round blade holder head connected to a support which can be translated and positioned along a beam or the like.
Said known cutting units are equipped with a system of ducts supplied by a pressurised fluid, generally air, which determines both the desired positioning of the cutting unit along the beam and the lowering of the blade during operation in relation to a counterblade.
The known cutting units, although fulfilling in a fairly satisfactory manner their functions, display considerable shortcomings and limitations. Thus for example in some cutting units replacement of the blade holder head in case of wear or other requires complicated and laborious operations by the operator. In other cutting units replacement of the blade holder head is fast but the structural means of engagement used are complicated and in time unreliable because subject to divers stresses during operation of the cutting units.
Another considerable shortcoming is that the cut-off blade is not adequately protected, in particular in the nonoperating position, so that it can cause undesired harm to the operator.
Another shortcoming of the known cutting units is that the blade holder head cannot be rotated around its axis so that in case of wear of the counterblade edge it is necessary to reposition the beam of the cutting unit to use the opposite edge of said counterblade. Said operation negatively affects the operating cycle of said cutting units.
In addition, the impossibility of rotating the blade holder head does not allow, e.g. for material cut-off requirements, performing the so-called "scissors" cut-off of changing the angular positioning of the blade in relation to the counterblade depending on the type of material to be cut off.